An old new word: shul. Stephen Batchelor (Buddhism Without Beliefs, in the chapter titled "Emptiness") defines and explains:

"Emptiness," said the Tibetan philosopher Tsongkhapa, in 1397, "is the track on which the centered person moves." The word he uses for track is shul. This term is defined as "an impression", a mark that remains after that which made it has passed by — a footprint, for example. In other contexts, shul is used to describe the scarred hollow in the ground where a house once stood, the channel worn through rock where a river runs in flood, the indentation in the grass where an animal slept last night. All these are shul: the impression of something that used to be there.

A path is a shul because it is an impression in the ground left by the regular tread of feet, which has kept it clear of obstructions and maintained it for the use of others. As a shul, emptiness can be compared to the impression of something that used to be there. In this case, such an impression is formed by the indentations, hollows, marks, and scars left by the turbulence of selfish craving. When the turmoil subsides, we experience tranquility, relief, and freedom.

To know emptiness is not just to understand the concept. It is more like stumbling into a clearing in the forest, where suddenly you can move freely and see clearly. To experience emptiness is to experience the shocking absence of what normally determines the sense of who you are and the kind of reality you inhabit. It may last only a moment before the habits of a lifetime reassert themselves and close in once more. But for that moment, we witness ourselves and the world as open and vulnerable.